1. Field of the Invention
The present invention relates to an etching end point detection window used in the fabrication of a liquid crystal display device to detect an etching end time accurately and a method of fabricating the etching end point detection window. Also, the present invention is directed to an etching end point detecting method for detecting an etching end time using the etching end point detection window.
2. Description of the Related Art
Generally, an active matrix type of liquid crystal display device displays a picture using a pixel (or picture element) matrix having pixels arranged at intersections between gate lines and data lines. Each pixel includes a liquid crystal cell controlling a transmitted light quantity in accordance with a voltage level of a data signal from the data line. Thin film transistors (TFTs) are installed at the intersections between the gate lines and the data lines to switch a data signal to be transmitted toward a liquid crystal cell in response to a scanning signal from the gate line.
Referring to FIG. 1, there is shown a TFT formed on a substrate 18. Hereinafter, a method of fabricating the TFT will be described. First, a gate electrode 20, made from Al or a metal film including Al or the like, is formed on the substrate 18. The gate electrode 20 is integral with a gate line(not shown). On the substrate 18 and the gate electrode 20, a gate insulating film 22 made of an inorganic film, such as SiNx, SiOx or the like, is provided.
A semiconductor layer 24 made from an amorphous Si, hereinafter referred to as a-Si, and an Ohmic contact layer 26 made from a-Si doped with N+ ions are sequentially deposited on the gate insulating film 22. A source electrode 28 and a drain electrode 30 made from a metal such as Cr, etc. are provided on the Ohmic contact layer 26 and the gate insulating film 22. The source electrode 28 is integral with a data line (not shown). The Ohmic contact layer 26 exposed through an opening between the source electrode 28 and the drain electrode 30 are removed by means of dry or wet etching. A protective film 32 made from SiNx or SiOx is deposited over the substrate 18 to cover the TFT. The protective film 32 has the same thickness on the substrate 18 and is deposited with an inorganic material.
In order to provide contact holes, a portion of the protective film 32 disposed on a pad of the drain electrode 30, the data line and the gate line are etched out. At this time, a pixel electrode 34 made from indium tin oxide is electrically connected, via a contact hole through the protective film 32, to the drain electrode 30. Output lines of drive circuits are electrically connected, via contact holes defined by the protective film 32, to the pads of the data line and the gate line, respectively.
As seen from the foregoing, etching is performed in forming the electrode pattern and the contact holes. And, because an etched area defined only by the pattern during the etching process is small, it is difficult to sense an etched depth accurately. Accordingly, as shown in FIG. 2, an end point detection (EDP) window 42 is provided at the outside of a display region 40, that is, a non-display region 19. A number of gate lines 2 and a number of data lines 3 are formed in a direction perpendicular to each other in the display region 40. TFTs 10 are formed at intersections between the gate lines 2 and the data lines 3. The non-display region 19 includes (1) the peripheral area of the display region 40 where pads 2a and 3a, formed at the ends of the gate lines 2 and the data lines 3, respectively, are located, (2) the edge area of the substrate 18, and (3) an area between the display regions 40. After fabrication of the TFTs 10 is completed, the display region 40 and the pads 2a and 3a are cut along a line 41 in such a manner that the display region 40 includes the pads 2a and 3a. 
FIG. 3A and FIG. 3B are sectional views taken along line IIIxe2x80x94III in FIG. 2 for the purpose of explaining an etching process for defining a contact hole at a pad of a gate line. As shown, a photo-resist pattern 44 is formed on the substrate 18 so as to define a contact hole 21a on the pad 2a of the gate line. Specifically, an EPD window 42 and a real pattern window 43 are formed in the photo-resist pattern 44 through exposure and development. The gate insulating film 22 and the protective film 32 are disposed between the EDP window 42 and the substrate 18. The pad 2a of the gate line, the gate insulating film 22 and the protective film 32 are disposed between the real pattern window 43 and the substrate 18. The substrate 18, patterned with the EDP window 42 and the real pattern window 43, is mounted within an etching chamber so as to form the contact hole 21a to the pad 2a of the gate line. SF6 gas is then injected into the etching chamber. At this time, an etchant including SF6 gas contacts the protective film 32 through the EDP window 42 and the real pattern window 43, and simultaneously begins to etch the protective film 32.
The etchant and the protective film 32 react to produce a nonvolatile gas SiF4. After the protective film 32 within the real pattern window 43 is removed, the gate insulating film 22 is removed to expose the pad 2a of the gate line. Also, the protective film 32 and the gate insulating film 22 within the EDP window 42 are removed to expose the substrate 18 under the EDP window 42. The concentration of SiF4 gas dramatically decreases or is no longer generated once the pad 2a of the gate line and the substrate 18 are exposed. Accordingly, an operator can determine an etching end time by sensing a concentration difference in or generation of SiF4 gas. Herein, the SiF4 gas evacuated during etching is converted into a voltage signal so that an operator can easily perform the sensing operation.
A liquid crystal display has the advantages of small dimensions (e.g., being slim) and low power consumption. And, studies for improving the liquid crystal display device are ongoing to further reduce power consumption. Recently, a scheme for overlapping the pixel electrode 34 with the data line 3 has become a prevailing technique. In this technique, in order to reduce a parasitic capacitance between the data line 3 and the superimposed pixel electrode 34, the protective film 32, formed between the pixel electrode 34 and the data line 3, is made from an organic substance with a low dielectric constant instead of an inorganic substance. For example, an organic material, such as Benzocyclobutene (BCB), is used as a material for the protective film 32.
Generally, the organic substance is grown into a film by spin-coating and thus the surface of the film becomes even. In this case, as shown in FIG. 4A, an organic protective film 46 exposed by the EPD window 42 is thicker than the film exposed by the real pattern window 43. Specifically, a relationship of a thickness t1 of the organic protective film 46 under the EPD window 43 to a thickness t2 of the organic protective film 46 under the real pattern window 43 is t1 greater than t2. Thus, after etching the organic protective film 46 to expose the pad 2a of the gate line, a portion of the organic protective film 46 exposed by the EPD window 42 remains. As shown in FIG. 4B, a thickness of Dt remains once the pad 2a of the gate line is exposed. As a result, there is only a slight variation in the amount of evacuated SiF4 gas once the pad 2a of the gate line is exposed, and it is difficult to determine an etching end point. Accordingly, as shown in FIG. 4C, the pad 2a of the gate line can become damaged from over-etching. Also the photoresist pattern 44 sticks onto the organic protective film 46 to cause a defect at the time of forming the pixel electrode 34.
Accordingly, it is an object of the present invention to provide an etching end point detection window in a liquid crystal display device that is capable of detecting an etching end time accurately.
A further object of the present invention is to provide an etching end point detecting method for detecting an etching end time by utilizing an etching end point detection window.
These and other objects are achieved by an intermediate liquid crystal display device product, comprising a real pattern formed on a substrate; a dummy pattern formed on the substrate, the dummy pattern having a same thickness as the real pattern; and a window definition layer defining an etching end point detection window over the dummy pattern.
These and other objects are further achieved by a method of forming an etching end point detection window, comprising forming a real pattern on a substrate; forming a dummy pattern having a same thickness as the real pattern on the substrate; and forming a window definition layer defining an etching end point detection window over the dummy pattern.
These and other objects are still further achieved by an etching end point detecting method, comprising forming a real pattern on a substrate; forming a dummy pattern having a same thickness as the real pattern on the substrate; forming a window definition layer which defines an etching end point detection window over the dummy pattern and an etch window over the real pattern; etching via the etching end point detection window and the etch window; detecting a reaction result from the etching step; and determining an etching end point based on output from the detecting step.